Income and Corporation Taxes Act 1988

2 (1) This paragraph has effect where a deduction falls to be allowed under section 193(1) in respect of the emoluments from an employment (“the relevant employment”) for a year of assessment in which the duties of—

(a) the relevant employment; or

(b) any other employment or employments held by the person concerned which are associated with the relevant employment,

are not performed wholly outside the United Kingdom.

(2) The amount of the emoluments from the relevant employment in respect of which such a deduction is allowed for the year of assessment shall not exceed such proportion of the emoluments for that year from the relevant employment and the other employment or employments (if any) as is shown to be reasonable having regard to the nature of and time devoted to the duties performed outside and in the United Kingdom respectively and to all other relevant circumstances.

(3) For the purposes of this paragraph an employment is associated with another if they are with the same person or with persons associated with each other and—

(a) a company is associated with another company if one of them has control of the other within the meaning of section 416 or both of them are under the control within the meaning of that section of the same person or persons,

(b) an individual or partnership is associated with another person (whether or not a company) if one of them has control of the other within the meaning of section 840 or both are under the control within the meaning of that section of the same person or persons;

but paragraph (b) above shall not be construed as requiring an individual to be treated in any circumstances as under the control of another person.